TEMPERATURE CONTROL APPARATUS, PROCESSING APPARATUS, AND TEMPERATURE CONTROL METHOD

• US 20090084771A1
• Filed: 09/25/2008
• Published: 04/02/2009
• Est. Priority Date: 09/28/2007
• Status: Active Grant

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: NOMURA, Masatoshi
• Granted Patent: US 8,188,407 B2
• Time in Patent Office: Days
• US Class Current: 219/263
• CPC Class Codes: G05D 23/1913 delivering a series of pulses
• CPC Class Codes: G05D 23/22 the sensing element being a thermocouple

Abstract

Disclosed is an temperature control apparatus including: a resistance heater a resistance value of which changes dependently on a temperature thereof; a fixed resistance connected to the resistance heater in series; a signal generator to output a control signal which has two voltage levels of a first voltage and a second voltage; a switching section to flow a current through the resistance heater and the fixed resistance when the voltage level is the first voltage, and not to flow a current through the resistance heater and the fixed resistance when the voltage level is the second voltage; and a first voltage measuring instrument to measure a voltage value across the fixed resistance at the time when the current flows through the fixed resistance, wherein the signal generator controls the temperature of the resistance heater based on the measured voltage by the first voltage measuring instrument.

Claims

1. An temperature control apparatus comprising:

a resistance heater having characteristics that a resistance value of the resistance heater changes dependently on a temperature thereof;

a fixed resistance connected to the resistance heater in series;

a signal generator to output a control signal which has two voltage levels of a first voltage and a second voltage;

a switching section to flow a current through the resistance heater and the fixed resistance when the voltage level of the control signal is the first voltage, and not to flow a current through the resistance heater and the fixed resistance when the voltage level of the control signal is the second voltage; and

a first voltage measuring instrument to measure a voltage value across the fixed resistance at the time when the current flows through the fixed resistance,

wherein the signal generator controls the temperature of the resistance heater based on the measured voltage by the first voltage measuring instrument.

2. The temperature control apparatus according to claim 1, wherein the fixed resistance has a smaller resistance value than the resistance value of the resistance heater.

3. The temperature control apparatus according to claim 2, wherein the resistance value of the fixed resistance is in a range from 0.06Ω

to 30 Ω

.

4. The temperature control apparatus according to claim 1, wherein:

the control signal is a pulse signal of certain period which has the two voltage levels of the first voltage and the second voltage; and

the signal generator is a PWM controller which controls a value of a duty ratio which is a ratio between a time when the control signal is in the voltage level of the first voltage and a time when the control signal is in the voltage level of the second voltage.

5. The temperature control apparatus according to claim 4, wherein the PWM controller obtains the temperature of the resistance heater based on the measured voltage by the first voltage measuring instrument at the time when the control signal output from the PWM controller is in the first voltage, and resets the duty ratio of the control signal to bring the temperature of the resistance heater close to a predetermined set temperature.

6. The temperature control apparatus according to claim 4, wherein the resistance heater and the fixed resistance are connected to each other in series, and a constant voltage is applied between terminals of the resistance heater and the fixed resistance through the switching section.

7. The temperature control apparatus according to claim 6, wherein the PWM controller calculates the resistance value of the resistance heater by a formula of (the resistance value of the resistance heater)={(the voltage value of the constant voltage)−

(the measured voltage by the first voltage measuring instrument)}×

(the resistance value of the fixed resistance)/(the measured voltage by the first voltage measuring instrument) to obtain the temperature of the resistance heater from the obtained resistance value based on resistance-temperature variation characteristics of the resistance heater, and changes the duty ratio of the control signal based on a difference between the obtained temperature of the resistance heater and a predetermined set temperature.

8. The temperature control apparatus according to claim 6 further comprising a second voltage measuring instrument to measure a voltage value across the resistance heater at the time when the current flows through the resistance heater,

wherein the PWM controller calculates the resistance value of the resistance heater by a formula of (the resistance value of the resistance heater)=(the measured voltage by the second voltage measuring instrument)×

(the resistance value of the fixed resistance)/(the measured voltage by the first voltage measuring instrument) to obtain the temperature of the resistance heater from the obtained resistance value based on resistance-temperature variation characteristics of the resistance heater, and changes the duty ratio of the control signal based on a difference between the obtained temperature of the resistance heater and a predetermined set temperature.

9. The temperature control apparatus according to claim 6, wherein the switching section is composed of a switching element connected to the resistance heater and the fixed resistance in series, the switching section includes a control terminal to which the control signal is applied, and the switching section is in on status when the control signal is in the first voltage and in off status when the control signal is in the second voltage.

10. The temperature control apparatus according to claim 6,

wherein the switching section includes:

a first switching element in which the constant voltage is applied to one terminal of a current path of the first switching element through a predetermined resistance element and the other terminal of the current path is connected to a ground voltage, the first switching section including a control terminal to which the control signal is applied, and the first switching element being in on status when the control signal is in the first voltage and in off status when the control signal is in the second voltage; and

a second switching element connected to the resistance heater and the fixed resistance in series, in which a control terminal thereof connected to a connecting node of the current path of the first switching element and the resistance element, and the second switching element being in on status when the control signal is in the first voltage and in off status when the control signal is in the second voltage.

11. A processing apparatus, supplied a raw material, subjected to temperature control thereof, causing a reaction or a phase change of the raw material, the apparatus comprising:

a processing device to cause the reaction or the phase change of the raw material; and

a temperature control apparatus including;

a resistance heater provided in the processing device to heat the processing device, the resistance heater having characteristics such that a resistance value of the resistance heater changes dependently on a temperature thereof;

a fixed resistance connected to the resistance heater in series;

a signal generator to output a control signal which has two voltage levels of a first voltage and a second voltage;

a switching section to flow a current through the resistance heater and the fixed resistance when the voltage level of the control signal is the first voltage, and not to flow a current through the resistance heater and the fixed resistance when the voltage level of the control signal is the second voltage; and

a first voltage measuring instrument to measure a voltage value across the fixed resistance at the time when the current flows through the fixed resistance,

wherein the signal generator controls the temperature of the resistance heater based on the measured voltage by the first voltage measuring instrument.

12. The processing apparatus according to claim 11, wherein the fixed resistance has a smaller resistance value than the resistance value of the resistance heater.

13. The processing apparatus according to claim 11, wherein:

the raw material is a liquid;

the processing device is a vaporizer to heat the raw material to vaporize it; and

the temperature control apparatus controls the temperature of the resistance heater to bring the temperature to close to a suitable temperature for vaporizing the raw material.

14. The processing apparatus according to claim 11, wherein:

the raw material is a mixture gas produce by vaporizing water and a liquid fuel including hydrogen in its composition;

the processing device is a reformer to produce a gas including the hydrogen by causing a reforming reaction of the raw material; and

the temperature control apparatus controls the temperature of the resistance heater to bring the temperature to close to a suitable temperature for causing the reforming reaction.

15. The processing apparatus according to claim 11, wherein:

the control signal in the temperature control apparatus is a pulse signal of certain period which has the two voltage levels of the first voltage and the second voltage; and

the signal generator is a PWM controller which controls a value of a duty ratio which is a ratio between a time when the control signal is in the voltage level of the first voltage and a time when the control signal is in the voltage level of the second voltage.

16. The processing apparatus according to claim 15, wherein the PWM controller in the temperature control apparatus obtains the temperature of the resistance heater based on the measured voltage by the first voltage measuring instrument at the time when the control signal output from the PWM controller is in the first voltage, obtains the temperature of the resistance heater based on resistance-temperature variation characteristics of the resistance heater, and resets the duty ratio of the control signal to bring the temperature of the resistance heater close to a predetermined set temperature.

17. The processing apparatus according to claim 15, wherein the resistance heater in the temperature control apparatus and the fixed resistance are connected to each other in series, and a constant voltage is applied between terminals of the resistance heater and the fixed resistance through the switching section.

18. The processing apparatus according to claim 17, wherein the switching section in the temperature control apparatus is composed of a switching element connected to the resistance heater and the fixed resistance in series, the switching section includes a control terminal to which the control signal is applied, and the switching section is in on status when the control signal is in the first voltage and in off status when the control signal is in the second voltage.

19. The processing apparatus according to claim 17, wherein

the switching section in the temperature control apparatus includes:

a first switching element in which the constant voltage is applied to one terminal of a current path of the first switching element through a predetermined resistance element and the other terminal of the current path is connected to a ground voltage, the first switching section including a control terminal to which the control signal is applied, and the first switching element being in on status when the control signal is in the first voltage and in off status when the control signal is in the second voltage; and

a second switching element connected to the resistance heater and the fixed resistance in series, the second switching element including a control terminal connected to a connecting node of the current path of the first switching element and the resistance element, and the second switching element being in on status when the control signal is in the first voltage and in off status when the control signal is in the second voltage.

20. A temperature control method for controlling a temperature of the resistance heater having characteristics that a resistance value of the resistance heater changes dependently on a temperature thereof, the temperature control method comprising:

outputting a control signal which has two voltage levels of a first voltage and a second voltage;

flowing a current through the resistance heater and the fixed resistance connected to the resistance heater in series when the voltage level of the control signal is the first voltage and shutting off a current flowing through the resistance heater and the fixed resistance when the voltage level of the control signal is the second voltage;

measuring a voltage value across the fixed resistance at the time when the control signal is in the first voltage; and

controlling the control signal based on the voltage value measured by the measuring step to control the temperature of the resistance heater.

21. The temperature control method according to claim 20, wherein:

the control signal is a pulse signal of certain period which has the two voltage levels of the first voltage and the second voltage; and

the controlling step includes controlling a value of a duty ratio which is a ratio between a time when the control signal is in the voltage level of the first voltage and a time when the control signal is in the voltage level of the second voltage.

22. The temperature control method according to claim 21,

wherein the controlling step includes:

calculating the resistance value of the resistance heater based on the voltage value measured by the measuring step;

obtaining the temperature of the resistance heater based on the calculated resistance value of the resistance heater and resistance-variation characteristics of the resistance heater relative to the temperature; and

changing the duty ratio of the control signal based on a difference between the obtained temperature value of the resistance heater and a predetermined set temperature.